Due to forces exerted on a workpiece, the worktable and workpiece supporting structures of such machines, distortions and misalignments occur. These result in inaccuracies in the dimensions and shape of the final machined article.
Where the dimensional errors are of the same order as the accuracy to which the article is to be machined it is impossible reliably to machine the article.
Distortions, misalignments and other error producing effects which can arise and tend to be cumulative must therefore be reduced to a level which is such that the magnitude of the cumulative error in the final article is much less than the error which can be permitted therein.
One of the primary controlling parameters in a machining operation is the accuracy with which the workpiece position relative to a machining tool is known. This parameter has been addressed and solutions proposed in our co-pending applications filed concurrently herewith. Other factors affecting accuracy are addressed in other copending applications.
It is an object of the present invention to provide an improved Z-axis drive for accurately moving a worktable and workpiece thereon, relative to a worktool in a machine tool.
The invention is of particular relevant to a cylindrical grinding machine.